1. Field of the Invention
The invention relates to forisomes, i.e., protein bodies which are also referred to as crystalline P-proteins, and which, according to the present knowledge in the art, are present exclusively, but ubiquitously, in plants of the legume family (Fabaceae, Papillionaceae). These protein bodies have very extraordinary, heretofore unknown, properties which enable their use as molecular working machines. Moreover, the invention relates to a method for isolating forisomes from their natural environment.
2. Description of the Related Art
The phloem of higher plants contains a system of microtubules (sieve elements) extending throughout the plant and serving for transporting photo assimilate (see FIG. 2). The sieve elements are comprised of cells that, as a whole, form a capillary system through the entire plant, i.e., the aforementioned phloem. This is a micro fluidic system having an inner pressure of up to 3.5 MPa and maximum flow velocities up to 3 cm/min−1.
Crystalline P-proteins are specific ingredient bodies of the sieve elements of the legume family of plants (Fabaceae). They were first observed in plant cuts and described as usually elongate compact structures up to a length of 30 μm with a highly ordered (“crystalloid”) ultra structure. Their function, however, remained unclear for more than a century after their discovery (Behnke, H. D., Nondispersive protein bodies in sieve elements: a survey and review of their origin, distribution and taxonomic significance; IAWA Bull, 12, 143-175 (1991)). In the meantime, it was found that they deform suddenly upon the occurrence of drastic changes of the hydrostatic pressure in the interior of the sieve elements. The proteins convert from an ordered “crystalloid” state (spindle shaped) (see reference numeral 2 in FIG. 2) into a “disperse” conformation that ultra-structurally appears to be less ordered (see reference numeral 1 in FIG. 2; in this Figure reference numeral 3 describes a sieve plate and reference numeral 4 the sieve elements). The dispersed form has a rounded configuration and forms plugs in the sieve tubes and reduces thus the further flow of the liquid rich with photo assimilates within the tube system. However, in this connection the protein bodies apparently do not lose their internal organization because they are still capable of spontaneously converting back to the ordered “crystalloid” state. A work group of the inventors was able to demonstrate that the observed confirmation changes in situ can be sufficiently explained by the dependency of the confirmation of crystalline P-proteins from certain divalent cations (Knoblauch, M., Peters, W. S., Ehlers, K. and van bel, A. J. E.; Reversible calcium-regulated stopcocks in legume sieve tubes. Plant Cell 13, 1221-1230 (2001)). The “crystalloid” state is present at Ca++ concentrations of significantly less than 1 μM, as can be adjusted with chelating agents, while concentrations in the micromolar range results in transformation into the “dispersed” conformation. With respect to the biological function of the protein bodies, they were given the name “forisomes”, derived from “foris” (Latin for door) and “soma” (Greek for body).